Electric kiln



1 J. scHmb-r 2,963,529

ELECTRIC KILN Filed Feb. 17, 1959 Q INVENTOR.

Ju/ius Selim/d7 AT ORN E United States Patent 71cc ELECTRIC KILN .lulius Schmidt, 4427 Walnut, Kansas City, Mo.

Filed Feb. 17, 1959, Ser. No. 793,844

Claims or. 13-22 Thisinvention relates to kiln structure and more partic ula rly, to a highly versatile, lightweight, low cost, electrically operated kiln adapted for various operations such as firing of ceramic ware and enamel coatings on products, as well as melting of nonferrous materials.

The primary object of the invention is to provide a portable kiln formed of a plurality of individual refractory units adapted to be disposed in stacked relationship presenting an article-receiving heating chamber within the stack, with certain of the refractory units carrying electrical resistance elements whereby the chamber may be heated to a predetermined temperature by the simple expedient of connecting the resistance elements to a suitable source of electrical energy.

A further important object of the invention is to provide a portable kiln .of the type referred to immediately above which may be readily assembled or disassembled without the use of tools or other implements by virtue of the fact that the refractory units are positioned in stacked relationship without interconnecting means of any kind being required.

An equally-important object of the invention is to provide an electric kiln having electrical resistance elements secured to thenormally innermost faces of at least two different refractory units forming a part of the kiln whereby the heat produced within the article-receiving chamber maybe changed byvarying the number of electricai resistance elements connected to the source of electrical energy or in the alternative, operably coupling the resistance elementsto the electrical powerline in either series or. parallel relationship, depending upon the amount of heat required to effect the firing or melting operation.

additional important aim of the invention is to provide a portable, electrically operated kiln which is constructed of a plurality of refractory bricks all of thesame size. and commercially available on the open market, whereby the kiln may be distributed at a minimum cost and without expensive machines being required in order to manufacturethe heating structure.

' Other important objects of the invention relate to the provision of a portable electric kiln wherein the individual refractory units adapted tobe disposed in stacked relationship are relatively lightin weight, and which may be compactly stacked for storage; to an electrically operated kiln which is adapted to be connected to a conveniently available source of electrical energy such as a power line of 115 volts and 30 amps. current, whereby the kiln may be usedat any convenient location; to a kiln wherein repair or replacement of any of the refractory units adapted to be disposed in stacked relationship to present the articlereceiving heating chamber, is facilitated by virtue of the fact that the units are not interconnected in any manner whatsoever during utilization of the same; and to other important objects and details of construction of the present kiln which will become obvious or be explained more fully as the following specification progresses.

In the drawing:

Figure 1 is an exploded, perspective view of a portable kiln bottom 14.

2,963,529 Patented Dec. 6, 1960 electric kiln embodying the principles of the present invention and illustrating the relative positions of the 111- dividual refractory units adapted to be disposed in stacked relationship topresent an article-receiving chamber within such stack;

Fig. 2 is an enlarged, perspective view of one of the corner sections of the portable kiln and showing the normally innermost face thereof;

Fig. 3 is an enlarged, vertical, fragmentary, cross-sectional view through the plug connector and associated portions constituting a part of one of the corner sections, taken .on the line 3-.3 of Fig. 1;

Fig. 4 is a schematic representation of the way in which the resistance elements of the portable kiln may be operably coupled with a power line in parallel relationship;

Fig. 5, illustrates by schematic representation the way in which such resistance elements may be coupled to the power line in series relationship if desired; and

Fig. 6 is an enlarged, fragmentary, sectional view taken on the line 66 of Fig. 1.

A portable, electrically operated kiln embodying the preferred concepts of the invention is illustrated in the drawing and broadly numerated 10. In order to maintain the cost of kiln 10 at a minimum figure as Well as imparting flexibility to the same it is to be preferred that a plurality of refractory bricks 12 be employed as the basic components of kiln 10. Refractory units or bricks 12 are preferably of the same size, insulating firebrick measuring 9 x 4 x 2 /2 being suitable. This firebrick is resistant to temperatures of at least 2600 F. and is relatively light in weight, each unit weighing only 2% lbs.

Portable kiln 10 may be furnished as a kit comprising a number of refractory units or bricks 12, thereby permitting the user of such kiln to arrange the bricks in predetermined relationship to present an article-receiving heating chamber of desired size. For purposes of illustration only, one kiln which may be formed from a plurality of refractory bricks 12 is shown in Fig. 1. In this type of kiln, six bricks 12 are disposed on a suitable supporting surface to thereby present a substantially rectangular In certain instances, it may be desirable to provide more than one layer of bricks 12 in forming kiln bottom 14, this being particularly true if the supporting surface for such kiln is in the nature of a Wooden table orfthe like. In any event, bricks 12 are merely disposed with certain margins thereof in abutting relationship and the same are not interconnected in any manner.

The side wall 16 of kiln 10 may be formed by a pair of opposed corner kiln sections 18 and 20 which are identical in construction, as well as a pair of spacer bricks 12a and 12b.

Inasmuch as corner sections 18 and 20 are identical in construction, only section 18 shown in Fig. 2 will be described in detail. It can be seen in this figure that section 18 comprises four bricks 12c, 12d, 12c and 12], with bricks 12c and 12a disposed with one longitudinal edge thereof in abutting relationship to corresponding longitudinal edges of respective units 12d and 12 and the narrow ends 22 of bricks 12c and 12d being disposed in abutting, overlapping relationship to onemajor rectangular face of corresponding bricks 12a and 12 The edge and face portions of bricks 12c,

across substantially the entire length and height of the innermost surface of corner section 18. As best shown in Fig. 2, groove 26 includes a pair of parallel groove portions 28 in each face 24 of bricks 12c, 12d, 12c and 12 and disposed in longitudinally extending relationship thereto. Furthermore, groove portions 28 in brick 120 are in direct alignment with groove portions 28 in b-rick 12c, while groove portions 28 in brick 12d likewise align with groove portions 28 in brick 12f. A cross groove portion 30 in bricks 12a and 12 remote from bricks 12c and 12d connect proximal extremities of groove portions 28 therein, while a groove portion 32 in bricks 12c and 12d interconnect parallel, opposed, proximal groove portions 28 of bricks 12c and 12d respectively.

An electrical resistance element broadly numerated 34 is provided on corner section 18 and preferably comprises an elongated length of high resistance wire such as an alloy wire containing 60 percent nickel, 24 percent iron, 16 percent chromium and 0.1 percent carbon and sold under the trademark Chromel A or an alloy wire containing 80 percent nickel and 20 percent chromium and sold under the trademark Nichrome disposed in serpentine groove 26. The length 38 of element 34 normally disposed in groove portions 28 of groove 26 are preferably spiral in longitudinal configuration, while the length 36 of element 34 located in cross groove portions 30 are of rectilinear configuration. Opposed end portions 40 and 41 of resistance element 34 extend through suitable passages (not shown) in respective bricks 12c and 12d and are operably coupled to an electrical connector 42 mounted on the normally outermost face of corner section 18. Connector 42 may comprise a pair of asbestos plates 44 and 46 maintained in parallel, horizontally spaced relationship by bolt and nut means 48 including respective bolts 49 extending through respective sleeves 50 positioned between plates 44 and 46. The heads 51 of bolts 49 are embedded within corresponding recesses 53 formed in bricks 12c and 12d at the zone of juncture thereof with refractory material placed in such recesses after heads 51 are inserted therein serving to maintain bolts 49 in laterally extending relationship to the outer faces of bricks 12c and 12d. Nuts 55 threaded over the outer ends of each of the bolts 49 serve to connect plates 44 and 46 to the outer faces of bricks 12c and 12d with plate 44 in flat, abutting relationship to the latter. It is to be understood that connector 42 may most conveniently be secured to corner section 18 at the time bricks 12c and 12d are joined by the cement referred to above.

Spaced, parallel prongs 52 are secured to and extend through plates 44- and 46, with the outermost ends of prongs 52 projecting outwardly from the outer face of plate 46 in substantially perpendicular relationship thereto. The end portions 40 and 41 of resistance element 34 are operably coupled with respective prongs 52 with nuts 54 threaded over the innermost ends of corresponding prongs 52 between plates 44 and 46 receiving the ends of respective wires therebetween. It is to be understood that prongs 52 are spaced sufiiciently so as to be received within a standard electrical receptacle forming a part of a line for operably coupling connector 42 to a suitable source of electrical energy such as power lines 56 and 58.

Upon disposition of corner sections 18 and 20 on kiln bottom 14 at opposed corners thereof, spacer bricks 12a and 12b are stacked in longitudinally upright positions closing the space between proximal opposed ends of corner sections 18 and 20.

Top 68 of kiln preferably comprises three units 12g, 12h and 121, interconnected at corresponding longitudinal edges thereof by cement, as defined above, and thereby of sufficient width to span the distance between opposed side portions of wall 16. In order to completely close the top of the chamber presented by botcemented units to a minimum, the flexibility of the portable kiln is maintained at a maximum to thereby permit the user to form an oven having a heating chamber of any predetermined size.

One of the units 12 presenting top 60, as for exam- 3 ple brick 12h, is provided with a passage 62 extending entirely transversely through the same in order to permit the user of kiln 10 to observe the interior of the heating chamber. A plug 64 adapted to be disposed on unit 12h in closing relationship to passage 62 prevents heat from escaping from the chamber during operation of kiln 10.

It is believed that the operation of kiln 10 is obvious from the above description, but it is to be pointed out that electrical connectors 42 are adapted to be coupled with power lines 56 and 58 in either parallel or series relationship as desired. In Fig. 4, the schematic representation shows how the connector 42 of section 18 may be coupled with respective power lines 56 and 58 by leads 66 and 68, while connector 42 of section 20- is also operably coupled with power lines 56 and 58 by respective leads 70 and 72. As an alternative arrangement, one prong 52 of the connector 42 of section 18 may be operably coupled with power line 58 by a lead 74, and the opposite prong 52 of the connector 42 of section 18 may be joined to one of the prongs 52 of the connector 42 of section 20 by a lead 76. The remaining prong 52 of connector 42 of section 20 is then coupled with power line 56 by a lead 78 to thereby place sections 18 and 20 in series relationship.

From the foregoing, it can be appreciated that the temperature to which the heating chamber within kiln 10 is raised during operation thereof may be changed by connecting sections 18 and 20 to power lines 56 and 58 in either parallel or series relationship. When high temperature is required, the parallel arrangement may be employed whereas when lower firing temperatures are expedient, the series coupling may be used.

It is also to be understood that after grooving and drilling of the bricks 12c, 12d, 12e and 12f from which corner sections 18 and 20 are connected, these brick units as well as the remaining bricks 12, including the cemented units 12g, 12h and 121', may be painted with a solution of diluted refractory mortar which subsequently hardens, thereby making units 12 wear-resistant and durable. The refractory mortar may be prepared by adding one part of refractory cement to three parts of water.

Upon stacking of refractory bricks 12 in a manner to present bottom 14, side wall 16 and top 60, the portable kiln thereby presented may be employed for various purposes such as firing ceramic ware, including pottery and sculptured figures, enamel coatings may be baked, and metals and alloys with a melting point below 2100 F. may be melted or otherwise subjected to heat treatment. In addition, kiln 10 may be utilized as a burn-out oven for lost wax casting procedures, as a drying oven and for other heat applications.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is:

'1. An electric kiln comprising a plurality of individual refractory units disposed in stacked relationship and presenting a bottom, a side Wall and a top defining an article-receiving chamber within the stack, the side wall in-' cluding a pair of opposed, horizontally L-shaped corner sections comprising a number of interconnected units and spacer units between proximal opposed, upright ends of the Corner sections, each of the corner sections being provided with grooves of serpentine configuration extending across the inner, angularly disposed faces thereof defining a portion of the chamber; electrical resistance elements secured to each of the corner sections within and extending the length of respective grooves, opposed ends of each of the elements extending through a respective corner section and terminating exteriorly thereof; and electrical means interconnecting the externally disposed ends of each of the elements for permitting coupling of the latter to a source of electrical energy.

2. An electric kiln as set forth in claim 1, wherein one of the units is provided with an opening therethrough permitting viewing of the interior of said chamber.

3. An electric kiln as set forth in claim 1 wherein said L-shaped units having the elements secured thereto are disposed on opposed sides of said kiln.

4. An electric kiln as set forth in claim 1 wherein said L-shaped units each include a number of substantially rectangular blocks having certain margins thereof disposed in abutting relationship, there being heat-resistant adhesive means interconnecting said abutting margins of the blocks.

5. An electric kiln as set forth in claim 1 wherein said electrical means interconnecting the externally disposed ends of each of the elements includes a plug connected to said externally disposed ends of each of the elements, each of said plugs having prong means constructed and arranged to be received in an electrical receptacle operably coupled with said source of electrical energy.

References Cited in the file of this patent UNITED STATES PATENTS 1,057,745 Kohn Apr. 1, 1913 1,413,678 Mofiat Apr. 25, 1922 1,555,542 Young Sept. 29, 1925 1,638,826 Brannigan Aug. 16, 1927 2,744,946 Lewicki May 8, 1956 

